Inkjet printers typically include an ink path from an ink supply to a nozzle path. The nozzle path terminates in a nozzle opening from which ink drops are ejected. Ink drop ejection is controlled by pressurizing ink in the ink path with an actuator, which may be, for example, a piezoelectric deflector, a thermal bubble jet generator, or an electrostatically deflected element. A typical printhead has an array of ink paths with corresponding nozzle openings and associated actuators, such that drop ejection from each nozzle opening can be independently controlled. In a drop-on-demand printhead, each actuator is fired to selectively eject a drop at a specific pixel location of an image as the printhead and a printing substrate are moved relative to one another. In high performance printheads, the nozzle openings typically have a diameter of 50 microns or less, e.g. around 35 microns, are separated at a pitch of 100-300 nozzle/inch, have a resolution of 100 to 3000 dpi or more, and provide drop sizes of about 1 to 70 picoliters or less. Drop ejection frequency is typically 10 kHz or more.
Piezoelectric inkjet print assemblies are described in U.S. Pat. Nos. 5,265,315, 4,825,227, 4,937,598, 5,659,346 and 5,757,391; and in published U.S. Patent Application No. 2004/0004649, the entire contents of each is hereby incorporated by reference herein.
It is sometimes desirable to print on food products. An edible ink for a piezoelectric ink jet printer is described in WO03/048260, the entire contents of which is hereby incorporated by reference.